At this point, it is necessary to reveal a little inside information about how scientists work, something the textbooks don't usually tell you. The fact is that scientists are not really as objective and dispassionate in their work as they would like you to think. Most scientists first get their ideas about how the world works not through rigorously logical processes but through hunches and wild guesses. As individuals they often come to believe something to be true long before they assemble the hard evidence that will convince somebody else that it is. Motivated by faith in his own ideas and a desire for acceptance by his peers, a scientist will labor for years knowing in his heart that his theory is correct but devising experiment after experiment whose results he hopes will support his position.
Boyce Rensberger, How the World Works, William Morrow, NY, 1986, pp. 17-18. Rensberger is an ardently anti-creationist science writer.